Touch-sensitive displays (also known as “touch screens” or “touchscreens”) are well known in the art. Touch screens are used in many electronic devices to display graphics and text, and to provide a user interface through which a user may interact with the devices. A touch screen detects and responds to contact on the touch screen. A device may display one or more soft keys, menus, and other user-interface objects on the touch screen. A user may interact with the device by contacting the touch screen at locations corresponding to the user-interface objects with which she wishes to interact.
Touch screens are becoming more popular for use as displays and as user input devices on portable devices, such as mobile telephones and personal digital assistants (PDAs). One problem associated with using touch screens on portable devices is the unintentional activation or deactivation of functions due to unintentional contact with the touch screen. Portable devices also provide external buttons, switches, etc. (collectively, “buttons”) that are subject to unintentional engagement due to jostling of the device in a pocket, bag or case in which it is carried. This is also a problem as such switches can activate important device functions such as power-off and power-on. Therefore, there is a need for portable devices that prevent unintentional activation or deactivation of functions that are associated with the engagement of buttons and/or touch-screen display user interface elements. Ideally, devices with these protective features would still provide users with efficient and user-friendly access to device features and applications.